Wideband Code Division Multiple Access (WCDMA) is a mobile radio access network standard specified by a 3rd Generation Partnership Project (3GPP) and used in third generation wireless data/telecommunication systems.
An enhanced uplink transmission capability from the user equipment nodes (UEs) to the radio transceiver base station (Node B) was introduced in Release 6 to 3GPP WCDMA. The enhanced uplink provides improved uplink packet-data support with reduced round trip delay, high bit-rate availability and increased cell capacity.
In 3GPP WCDMA, the Radio Resource Control (RRC) protocol handles the control plane signalling between the UEs and the network. A UE can operate in one of a number of RRC states or modes. For example, a UE can operate in RRC idle mode when it has no connection. In connected mode, a UE can be directed to operate in a CELL_DCH (Dedicated Channel) state, a CELL_FACH (Forward access channel) state, a CELL_FACH (Cell Paging channel) state, or a URA_PCH (URA Paging channel) state.
As defined by 3GPP WCDMA Release 6, during a CELL_DCH state, a network node allocates dedicated resources for each UE.
Enhanced Uplink refers to a 3GPP mobile telephony protocol with increased uplink speeds, for example, up to 5.76 Mbit/s. The Enhanced Uplink feature is intended to improve the performance of uplink dedicated transport channels by increasing capacity and throughput and reducing delay.
When a UE transmits using the Enhanced Uplink protocol, it transmits data and control information on at least 3 physical channels, namely, the Dedicated Physical Control CHannel (DPCCH), the Enhanced-DPCCH (E-DPCCH), and the Enhanced Dedicated Physical Data CHannel (E-DPDCH). The DPCCH carries pilot bits that are known by the Node B as well as Layer 1 control information. The pilot bits are used as a reference by the Node B to estimate the radio channel conditions (e.g. searcher, channel estimation, frequency offset estimation, and signal to interference ratio). The E-DPCCH carries control information related to the enhanced dedicated physical data channel. The E-DPDCH carries the data bits.
Currently, UEs may sometimes fail when changing the CELL_FACH state to the CELL_DCH state, which may reduce the performance of the network.